Field of the Invention
The present invention relates to a method for separating at least two bridges of a segmented transport system for printing materials, in which the transport system includes a segmented electric linear drive, the electric linear drive includes a first and a second primary part, each primary part is constructed as a segmented longitudinal stator, the electric linear drive has a plurality of secondary parts constructed as carriages, and in each case a secondary part assigned to the first primary part and a secondary part assigned to the second primary part are coupled by a crossmember and, together with the crossmember, form a movable bridge of the transport system. Such an arrangement is usually called a gantry system. Furthermore, the present invention relates to an apparatus for implementing the method, having a segmented transport system for printing materials, the transport system including a segmented electric linear drive, the electric linear drive including a first and a second primary part, each primary part being constructed as a segmented longitudinal stator, the electric linear drive having a plurality of secondary parts constructed as carriages, and in each case a secondary part assigned to the first primary part and a secondary part assigned to the second primary part being coupled by a crossmember and, together with the crossmember, forming a movable bridge of the transport system. Additionally, the present invention relates to a machine for processing printing material, for example a printing press, in particular a sheet-processing rotary printing press for lithographic offset printing or, for example, a further print processing machine.
In machines in the so-called graphic industry (prepress stage, print production and further print processing), printing materials, for example sheets of paper, board or film, are conveyed and processed, for example printed, varnished or punched. The in-register conveyance of the printing materials in such machines, for example in sheet-fed printing presses or sheet punches, is normally carried out through the use of rotating transport cylinders or linear drive systems. Suitable linear drive systems are, for example, chain conveyors or electric linear drives, which is to say systems in which a rotor or carriage moves along a stator in accordance with the dynamo-electrical interaction between the rotor and a magnetic field which travels along the stator.
Electric linear drives for the sheet transport firstly have, on one side of the machine, a so-called primary part (stator) and, secondly, in each case so-called secondary parts (rotors) in each case assigned to one of the two primary parts. In each case, two rotors are coupled to each other through a crossmember, with the crossmember being constructed as a gripper bar for the printing material. German Patent DE 197 48 870 C2, corresponding to U.S. Pat. Nos. 5,809,892; 6,044,760; 6,092,801; and 6,240,843, describes a printing press having such an electric linear drive system.
Linear drive systems are normally constructed in segmented form, which means that the transport path is composed of a plurality of segments following one another. When the machine is switched off, it is possible for a problem to occur in which two or more gripper bars come to lie in one and the same segment of the linear drive system and then, when the machine is restarted, can no longer readily be moved individually under control. The same problem can occur when an emergency stop is carried out because of a disruption or when gripper bars are displaced manually during maintenance work. Such collided gripper bars must be divided or separated from one another again. However, manual separation requires a great deal of time and does not readily provide the necessary security of separation, which means that additional visual inspections are required.
German Published, Non-Prosecuted Patent Application DE 31 45 263 A1, which is not to be attributed to the graphic industry sector, describes the separation of workpieces (rods) which are moved forward by two segmented linear drives and are detected by switches. That separation operation is carried out by an individual piece being loosened from a bundle of workpieces by briefly switching over the traveling field direction and being picked up and transported away by an empty segment.
German Published, Non-Prosecuted Patent Application DE OS 22 58 492, corresponding to U.S. Pat. No. 3,771,463, likewise not to be attributed to the graphic industry sector, describes a pneumatic control system in which the speed and the spacing of vehicles from one another is maintained, with a guide being subdivided into control sections (stop blocks, slow blocks and fast blocks) and being provided with detectors. Patent Abstracts of Japan JP 63-99702 A describes a similar system for avoiding collisions of carriages of a linear drive. Patent Abstracts of Japan JP 01-264503 A describes a system for avoiding collisions in vertical transport paths with power interruption.